The present invention relates to a refrigeration unit with a thermal breaker and to the thermal breaker itself. More particularly, the present invention relates to a refrigeration unit with a thermal breaker that is a component used in preventing condensation from forming on the outer shell of the refrigeration unit in high humidity environments.
As known, the refrigerated wall of the refrigerated compartment of a refrigeration unit is maintained at a much lower temperature than the atmosphere outside the refrigerated compartment. As shown in FIGS. 2A, 2B and 2C, the outer shell of a typical refrigeration unit includes exterior panels 13 formed of a layer of sheet metal. As shown in FIGS. 2A, 2B and 2C, a metal panel 15 defines an inside surface the refrigerated compartment. A metal panel 16 forms a border around the opening of the refrigerated compartment and is exterior to the refrigerated compartment but in close proximity to panel 15. The panels 13, 15 and 16 encase heat-insulating material 14 to form the heat-insulating walls of the refrigeration unit.
Since metal evenly conducts heat, a continuous metal panel extending both inside the refrigerated compartment and outside the refrigerated compartment as part of a heat-insulating wall of the refrigerated unit would tend to maintain itself at the same equilibrium temperature. As shown in FIGS. 2A, 2B and 2C, a thermal break member 17 is fitted as a part of the refrigeration unit that connects compartment panel 15 with front panel 16. Moreover, thermal break member 17 is formed of material that is a poor conductor of heat. Rigid polyvinylchloride is a typical material for forming thermal break member 17.
In environments where the refrigeration unit is subjected to high humidity, as shown in FIGS. 2A, 2B and 2C, a so-called anti-sweat heater wire 18 is provided and disposed to contact front panel 16. The purpose of such wire 18 is to keep front panel 16 warm enough to prevent condensation from forming on the exterior surface of panel 16. As shown in FIGS. 2A and 2C, sometimes heater wire 18 is nestled within a conduit that is formed at least in part by thermal break member 17. In FIG. 2A, the conduit housing heater wire 18 is formed in part by a forward lip portion 19 of thermal break member 17 and a recessed portion of front panel 16. As shown in FIG. 2B, the conduit is formed by a length of tape 26 that adheres heater wire 18 to the inside surface of front panel 16. As shown in FIG. 2C, thermal break member 17 is formed by two interlocking components 20 and 21. The conduit is formed in part by a forward lip portion 19 of an interlocking cap component 21, a forward edge of an interlocking panel component 20 and a flange portion 22 of front panel 16 wherein flange portion 22 is disposed at a right angle with respect to front panel 16 and parallel to inner panel 15.
Arrangements such as shown in FIGS. 2A, 2B and 2C are effective in preventing condensation from forming on the exterior surface of front panel. 16 of a refrigeration unit so long as electric current can be provided to flow through heater wire 18. However, circumstances can cause malfunctions of heater wire 18, and require replacement of same. For example, a power surge could burn out a portion of heater wire 18, or heater wire 18 could merely wear out. Once heater wire 18 malfunctions, condensation forming on the exterior surface of front panel 16 would alert the repairman of the need to replace heater wire 18.
Replacement of heater wire 18 is a major undertaking for each of the configurations shown in FIGS. 2A, 2B and 2C. In the embodiment shown in FIG. 2A for example, thermal break member 17 must be removed by applying force against the inside edge 23 via a block 24 of wood and using a hammer 25 to strike the block 24. In this way, lip portion 19 of thermal break member 17 is forced to move away from the recess of front panel 16 and thereby expose heater wire 18 so that heater wire 18 can be replaced. Upon replacement of heater wire 18, block 24 must be placed against lip portion 19 and struck with hammer 25 to reposition thermal break member 17 back into its prior orientation as part of the wall of the refrigeration compartment. In some instances, too much damage is done to the original thermal break member 17 for it to be reused, and a new piece of thermal break member 17 must be used to replace the damaged member.
In the FIG. 2B embodiment, rigid polyurethane foam 14 is molded in place after heater wire 18 is attached via adhesive tape 26 to the inside surface of front panel 16. If heater wire 18 malfunctions, it cannot be replaced without destroying thermal break member 17 and removing polyurethane foam 14 from within the compartment wall. Once heater wire 18 is replaced, polyurethane foam must be reintroduced, and a replacement thermal break member 17 must be provided and re-inserted as part of the wall of the refrigerated compartment. This replacement process is very labor-intensive and time consuming and cannot be done in the field.
In the FIG. 2C embodiment, thermal break member 17 comprises two interlocking components 20 and 21. Panel component 20 is configured in a manner similar to thermal break member 17 shown in FIG. 2B. However, panel component 20 is provided with a portion that faces toward the refrigerated compartment when disposed to connect between inside panel 15 and front panel 16. The inner portion of panel component 20 is configured to receive thermal break cap component 21 so that cap component 21 mechanically attaches in a friction fit to panel component 20. Moreover, when cap component 21 is attached to panel component 20, a conduit is formed to receive heater wire 18 therein. This conduit that receives heater wire 18 is formed in part by compartment panel 15, thermal break cap 21, and panel component 20. Replacement of heater wire 18 requires disengagement of thermal break cap 21 from panel component 20 of thermal break member 17. This is accomplished by inserting a wedge such as a screwdriver blade between compartment panel 15 and the edge of thermal break cap 21 and prying thermal break cap 21 away from the friction fit interlock with panel component 20. Once thermal break cap 21 is removed, malfunctioning heater wire 18 can be removed and replaced with a new heater wire 18. Thereafter thermal break cap 21 can be reinserted over panel component 20 and locked thereto by the application of sufficient force to deform the mating components of panel component 20 and thermal break cap 21 until they interlock with one another. Replacement of heater wire 18 in the FIG. 2C embodiment can be accomplished without destroying thermal break member 17 and in a much faster manner than is possible with the embodiments shown in FIG. 2A or FIG. 2B. However, the two-piece thermal break member 17 shown in FIG. 2C is much more expensive to manufacture due to the need for precise tolerances in order to effect the proper interlock between the two components 20 and 21. Moreover, the assembly process for the refrigeration unit requires an additional step to attach the thermal break cap 21 to panel component 20. In addition, manufacturing of the refrigeration unit is rendered more complicated and therefore more costly due to the need to inventory two separate components 20 and 21 for thermal break member 17 in the FIG. 2C embodiment.
Thus, a need exists to provide a thermal break member that is less costly to install and maintain, and at the same time facilitates replacement of the heater wire in a manner that is economical. Such replacement should be capable of being done with relatively little skill by the repairing personnel, without requiring large amounts of the repair person's time, and without destruction of the thermal break member in the process of replacement of the heater wire.